Be it known that I, Les Johnson, a citizen of the United States, residing at 218 Brett Drive, Madison, Ala. 35758, and Gregory Matloff, a citizen of the United States, residing at 417 Greene Avenue, Brooklyn, N.Y. 11216, have invented a new and useful xe2x80x9cCombination Solar Sail And Electrodynamic Tether Propulsion System.xe2x80x9d
The present invention relates generally to systems and methods for traveling through space. More particularly, this invention pertains to a system and method for traveling through space using solar sails and electrodynamic tethers.
Solar sail propulsion systems for traveling through space are known in the art. For example, the document entitled xe2x80x9cInterstellar Exploration: Propulsion Options For Precursors And Beyond,xe2x80x9d authored, in part, by the first applicant of the present invention, teaches the use of a solar sail propulsion system to propel a spacecraft through space. Another document, entitled xe2x80x9cA Solar Sail Design For A Mission To The Near-Interstellar Medium,xe2x80x9d discloses a specific design for a solar sail propulsion system to propel a spacecraft into near-interstellar space. In addition, U.S. Pat. No. 4,614,319, issued to Drexler on Sep. 30, 1986 and entitled xe2x80x9cSolar Sail,xe2x80x9d also teaches the use of a solar sail propulsion system. The contents of the above-referenced documents are hereby incorporated by reference into this application.
Solar sail propulsion systems typically include a large, flat, thin, reflective material supported by a lightweight deployable structure. These systems generate propulsion by transferring the momentum of solar photons reflected by the solar sail to the sail. In other words, propulsion is generated when sunlight strikes and is reflected off of the solar sail.
Solar sail propulsion systems have several advantages. First, such systems do not require the use of propellants to generate propulsion. As a result, a spacecraft can be made lighter or, alternatively, the spacecraft payload carrying capacity can be increased. Second, systems using solar sails to generate propulsion can reach speeds that are much faster than speeds reached by conventional propellant-type propulsion systems. As a result, solar sail propulsion systems can reach planets far away from the Earth in a much shorter time period.
Unfortunately, solar sail propulsion systems also have a significant disadvantage. Solar sails rely on the sun, and the sunlight that it produces, for propulsion and cannot generate sufficient thrust when the solar sail moves too far away from the sun, typically approximately 5 Astronomical Units (AU). As a result, solar sails cannot be used to steer a spacecraft into orbit or to perform orbital maneuvers around a planet, such as Jupiter or Saturn, which is very far away from the sun.
Furthermore, conventional propellant-type propulsions systems, which might be used to steer a spacecraft into orbit or to perform orbital maneuvers around such a planet, are not a desirable solution to this problem because these systems require the use of propellants. Recall that one of the primary advantages of using a solar sail propulsion system is to eliminate the necessity of carrying propellants on the spacecraft. If a conventional propellant-type propulsion system were used, then one of the primary advantages of using a solar sail propulsion system would be lost.
What is needed, then, is an improved solar sail propulsion system that provides sufficient propulsion to steer a spacecraft into orbit and to perform orbital maneuvers around planets that are so far away from the sun that the solar sail is no longer effective.
Accordingly, one object of the present invention is to provide an improved solar sail propulsion system that provides sufficient propulsion to steer a spacecraft into orbit and to perform orbital maneuvers around planets that are so far away from the sun that the solar sail is no longer effective.
Another object of the present invention is to provide an improved solar sail propulsion system that does not require the use of propellants to steer a spacecraft into orbit and to perform orbital maneuvers around planets that are so far away from the sun that the solar sail is no longer effective.
These and other objects, which will become apparent to someone practicing the present invention, are satisfied by the present invention of a combination solar sail and electrodynamic tether system. The combination solar sail and electrodynamic tether system includes a solar sail system for propelling a spacecraft through space using solar photons and an electrodynamic tether system for steering the spacecraft into orbit and through orbital maneuvers around a planet using the planet""s magnetic field.